Many complex solutions have been developed over time to provide processing redundancy. Many of these solutions rely on having either one system backing up several, or several systems backing up one system. Solutions which provide m for n redundancy often require complex configuration and coordination. In addition, for packet inspection services which require knowledge of subscriber state, additional protocol processing and operation is often required to recreate the subscriber state, often with concomitant delays in recovering operation.
VRRP or Virtual Router Redundancy Protocol is a protocol which allows several routers on a multiaccess link to utilize the same virtual IP address. VRRP is designed to eliminate the single point of failure inherent in the static default routed environment. The VRRP router controlling the IP address(es) associated with a virtual router is called the master, and forwards packets sent to these IP addresses. The master router is elected with the other routers acting as backups in case of the failure of the master router. Any of the virtual router's IP addresses on a LAN can then be used as the default first hop router by end-hosts. The advantage gained from using VRRP is a higher availability default path without requiring configuration of dynamic routing or router discovery protocols on every end-host. Using VRRP allows host systems to be configured manually or via Dynamic Host Configuration Protocol (DHCP) with a single default gateway, rather than running an active routing protocol. DHCP is the protocol for automating the configuration of computers that use Transmission Control Protocol/Internet Protocol (TCP/IP). VRRP provides a function similar to a Cisco Systems, Inc. proprietary protocol named Hot Standby Router Protocol (HSRP) and with a function similar to a Digital Equipment Corporation, Inc. proprietary protocol named IP Standby Protocol. VRRP provides only m backups (m redundancy) for each one primary unit. This m for 1 redundancy presents significant limitations as to redundancy possibilities and situations. VRRP also does not optimally utilize the redundant units.